Apparently, the Covenant are making a mistake that, in their own culture, is about as bad as it gets.

It is, I think, quite clear that humanity is, or once was, Forerunner. This is evidenced by the fact that Covenant technology is stolen Forerunner tech ("They own nothing which they have not stolen", i think was the quote from the Cortana letters)-alluded to heavily in "the Flood". Assuming that this is true, and the Covenant have not improved upon Forerunner technology, then that would explain how the MJOLNIR project actually DID improve upon Covenant shield technology (see "the Fall of Reach").

Assuming that the Covenant worship the Forerunner, and assuming that Humanity is descended from the Forerunner, and assuming that this is developed in Halo 2, who thinks that the Covenant are in for one hell of a guilt trip, eh? ;-)